Peak Vision XD9 Dual-Zone Hybrid Golf Sunglass Dual zone technology optimizes vision across lighting extremes PEAKS Dual-Zone/Zero Distortion Lens Technology; No bi-refringent distortion; Reduced Chromatic Aberration (Lens Clarity, high 45 abbe value) Polycarbonate Lenses exhibit significant optical errors; Bi-refringent (Appears as rainbow); Chromatic Aberration (Lens Haziness poor 28 abbe value